Gnathostomiasis

What is gnathostomiasis?

Gnathostomiasis is a zoonosis (an infection passed on from animals) caused by larvae of a nematode (unsegmented roundworm). The most common cause is Gnathostoma sinigerum. Other species include G hispidum.

Cutaneous gnathostomiasis is known by various names in across the world including:

Yangtze River oedema

Shaghai rheumatism

Tuao chid

Panniculitis nodular migratory filica

Who gets gnathostomiasis?

Gnathostomiasis is endemic in countries where food is eaten raw or is undercooked. These countries include: South East Asia, Japan, Latin America, China, India, and Africa. The first Australian case was confirmed in 2011 in Western Australia.

Gnathostomiasis is rare. However, the diagnosis should considered in people with cutaneous lesions and eosinophilia that have recently travelled in endemic countries.

What causes gnathostomiasis?

Gnathostomiasis is caused by ingesting larvae in improperly cooked foods such as fish, chicken, snakes and frogs. Typically, sushi does not pose a risk of gnathostomiasis, as more expensive saltwater fish do not carry the larvae.

In humans, intermittent symptoms appear when the late third-stage larvae migrate through the tissues. The larvae cannot reach sexual maturity in a human host.

What are the clinical features of gnathostomiasis?

Generalised symptoms may develop within 24–48 hours after consuming the larvae. Such symptoms include:

These symptoms may last for 2–3 weeks, as the larva migrates through the wall of the stomach, intestines or liver.

Cutaneous gnathostomiasis

Cutaneous gnathostomiasis presents as linear non-pittingoedema.

It may be erythematous, pruritic or painful.

Usually it is solitary, however multiple lesions have been reported.

The most common sites are the trunk or upper limbs.

The larvae leave tracking marks and subcutaneous haemorrhages.

Lesions are seen on the face are associate with central nervous system or ocular spread.

Visceral gnathostomiasis

Visceral disease is due to migration of gnathostomiasis larvae within the body

Pulmonary symptoms

Cough

Pleuritic chest pain

Haemoptysis

Pneumothorax

Lobar consolidation or collapse

Gastrointestinal symptoms

Sharp pains

Can be mistaken for appendicitis or intestinal obstruction

Genitourinary symptoms

Uncommon

Haematuria

Passage of larvae in urine

Haematospermia

Vaginal bleeding

Ocular symptoms

Uveitis

Iritis

Glaucoma

Retinal scarring

Retinal detachment

Auricular symptoms

Mastoiditis

Sensorineural hearing loss

Central nervous system (CNS)

Potentially lfe-threatening

Subarachnoid haemorrhage

Coma

Brain stem involvement: respiratory failure

Eosinophilic meningitis.

CNS disease can present as progressively worsening disease over several days. Symptoms include:

Incontinence

Loss of sensation

Headaches

Radicular pain in the limbs

Weakness or partial paralysis of limbs

How is gnathostomiasis diagnosed?

Gnathostomiasis is diagnosed by serology in blood or cerebrospinal fluid (CSF) when CNS is involved.

It may be suspected in the presence of significant blood or CSF eosinophilia (up to 50% of total white cell count). Note that eosinophilia disappears in chronic disease when larvae enter subcutaneous tissues.

What is the treatment for gnathostomiasis?

What is the outcome for gnathostomiasis?

If cutaneous or visceral gnathostomiasis is left untreated, the larvae may continue to cause intermittent symptoms until they die, which can be up to 12 years. The patient is considered clear of disease if asymptomatic for 12 months after treatment, eosinophilia has resolved and ELISA levels have decreased.

Relapse can occur up to 7 months after treatment, necessitating retreatment and close follow-up. There is a high mortality rate for patients with CNS involvement.